The only problem with f.lux is that it's so seamless it's like it's not running, so occasionally I'll turn it off accidentally and it feels like looking into the heart of a supernova.

My eye strain ended permanently about 4 years ago, the day I installed f.lux. My eyes have never once felt strained at night after that day. Truly a miracle program.

I recommend f.lux too. The only problems I've encountered with it are:

- doesn't take into account wacky sun hours in nordic countries during winter, I get around this by setting my location to be somewhere else

- isn't able to automatically detect when I'm playing a fullscreen videogame, when I would prefer it automatically switch off

- every now and then I'll edit a photo, upload it somewhere, and then get very confused about why it looks so weird when showing it to somebody on my phone -- it would be great if f.lux shut off when certain user-configurable applications are in focus

This is what's kept me from using it, I'm often jumping in and out of photoshop.

I don't know about windows, but a recent-ish update on OSX added the ability to disable per application.

http://i.imgur.com/AwDJYyX.png

Is anyhthing known about the internals of it, i.e. what code does it use? Something like SetDeviceGammaRamp on Windows? Or does it talk directly to the video card driver (if that is even possible in a generic way)? Or the monitor? Does it still work reasonably if I already have set my display to low brightness etc?

edit also wondering: it cannot know if I'm sitting in a completely dark room, a sunlit room or a room at night with fluorescent lighting. Don't such factors change what the ideal color would be? (not that I am constantly adjusting my display now according to the amount of clouds outside, just wondering what it does exactly. There's like no info whatsoever?)

Not sure how it works for Windows but the Linux source is available which could give you an idea:

https://github.com/Kilian/f.lux-indicator-applet

There's also redshift, an open source version that works on linux.

And for Android, there's "Twilight" :)

Wonderful tools